1. Field of the Invention
The present invention is generally related to an oil supply system for a marine engine and, more particularly, to a marine engine with a main lubricant conduit, or gallery, which is cooled by its proximity to a water conduit of the engine.
2. Description of the Related Art
Many different techniques have been used to reduce the operating temperature of lubricating oil used in a marine engine. Typically, these cooling techniques relate to the use of cooling water to reduce the temperature of an oil sump.
U.S. Pat. No. 6,619,274, which issued to Miyashita et al. on Sep. 16, 2003, describes an outboard engine intake air cooling system. An air intake cooling system for an outboard motor is equipped with a V-type engine is described. In one embodiment, the air intake cooling system has an air intake manifold and a water-cooling passageway positioned in the air intake manifold for cooling air in the air intake manifold. This system further has a water sleeve for cooling a main oil reservoir located inside the V-type engine, the water sleeve being positioned next to the main oil reservoir and connected to the water cooling passageway.
U.S. Pat. No. 6,868,819, which issued to Saiga et al. on Mar. 22, 2005, describes a lubricating system for an outboard motor. In one embodiment, the lubricating system has an oil pump positioned near the bottom of the engine, the oil pump driven by an oil pump rotor that is positioned at a connection between the crankshaft and an engine driven shaft. The oil pump is linked to the crankshaft. The system further includes a cam shaft driving mechanism for transmitting the rotation of the crankshaft to a propulsion device. The cam shaft driving mechanism is also positioned at the connection between the crankshaft and the driveshaft and is also linked to the crankshaft. The lubrication system also has a main oil tank for storing lubricating oil circulated by the oil pump and an engine cooling water passageway positioned next to the main oil tank. Another element of this embodiment of the lubricating system is a filter mounting base positioned on an outer wall of the cylinder blocks. The system also has oil passageways positioned at the bottom of the cylinder blocks for distributing the oil.
U.S. Pat. No. 6,834,635, which issued to Yomo et al. on Dec. 28, 2004, describes an outboard motor which includes an engine, an engine holder disposed below the engine, a driveshaft housing which is disposed below the engine holder, an intake device including an intake manifold disposed to a side surface of the engine, a lubricant supply device for supplying lubricant oil to the engine, an oil filter disposed below the intake manifold, and an oil cooler arranged below the intake manifold and between the engine and the oil filter. The oil cooler includes a casing and a cooler body disposed inside the casing and the casing is formed with a cooling water flowing-in union and a cooling water flowing-out union disposed in correspondence with the cooling water flowing-in union.
U.S. Pat. No. 6,358,108, which issued to Murata et al. on Mar. 19, 2002, describes an outboard motor which includes a first case and a second case disposed below the first case. The first case houses therein an oil pan and an upper part of a driveshaft. Within the oil pan, engine oil is held. The second case has its upper edge portion coupled to a lower edge portion of the first case. The arrangement prevents the oil pan from being affected by heat of the exhaust gas. Thus it becomes possible to prevent the engine oil held within the oil pan from increasing in temperature.
U.S. Pat. No. 6,067,951, which issued to Kitajima on May 30, 2000, describes an engine for an outboard motor. The cooling and exhaust systems for the engine are formed with a minimum number of components and ceiling joints. The flow of cooling the water to and from the engine is controlled so that the exhaust gas interchange area between the powerhead and the driveshaft housing will be well cooled, as will the oil reservoir for the engine and the oil returned to it.
U.S. Pat. No. 6,305,999, which issued to Toyama et al. on Oct. 23, 2001, describes an outboard motor that includes an engine holder, an engine which is disposed above the engine holder in a state of the outboard motor mounted to a hull in which a crankshaft extends substantially perpendicularly, and an oil pan disposed below the engine holder. A cooling water passage is formed in the oil pan and a driveshaft housing to guide the cooling water pumped up by the water pump to the engine. A relief valve is disposed on the way of the cooling water passage so as to discharge the cooling water into the exhaust chamber.
U.S. Pat. No. 6,416,372, which issued to Nozue on Jul. 9, 2002, describes an outboard motor cooling system. It includes an improved construction for enhancing cooling of the lubrication system. An oil pan depends from an engine of the outboard motor and into a driveshaft housing. A periphery coolant jacket is provided around the oil pan. A water pool is defined between the oil pan and the driveshaft housing. An exhaust manifold passes through in a hollow of the oil pan and a water curtain is defined between the hollow wall and the exhaust manifold. An upstanding water passage is also disposed through the oil pan. The oil pan therefore is sufficiently cooled.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be beneficial if a system could be provided that provides additional cooling to the lubricating oil of an outboard motor engine by other than the traditional methods which utilize oil coolers or cooling systems which cool the oil while it is within the oil sump of the outboard motor.